[PATCH v3 12/15] KVM: Add KVM_EXIT_MEMORY_ERROR exit

Chao Peng
2021-12-21T15:13:45Z

This new exit allows user space to handle memory-related errors.
Currently it supports two types (KVM_EXIT_MEM_MAP_SHARED/PRIVATE) of
errors which are used for shared memory <-> private memory conversion
in memory encryption usage.

After private memory is enabled, there are two places in KVM that can
exit to userspace to trigger private <-> shared conversion:
- explicit conversion: happens when guest explicitly calls into KVM to
map a range (as private or shared), KVM then exits to userspace to
do the map/unmap operations.
- implicit conversion: happens in KVM page fault handler.
* if the fault is due to a private memory access then causes a
userspace exit for a shared->private conversion request when the
page has not been allocated in the private memory backend.
* If the fault is due to a shared memory access then causes a
userspace exit for a private->shared conversion request when the
page has already been allocated in the private memory backend.

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
include/uapi/linux/kvm.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a2c1fb8c9843..d0c2af431cd9 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -297,6 +297,18 @@ struct kvm_tdx_exit {
} u;
};

+struct kvm_memory_exit {
+#define KVM_EXIT_MEM_MAP_SHARED 1
+#define KVM_EXIT_MEM_MAP_PRIVATE 2
+ __u32 type;
+ union {
+ struct {
+ __u64 gpa;
+ __u64 size;
+ } map;
+ } u;
+};
+
#define KVM_S390_GET_SKEYS_NONE 1
#define KVM_S390_SKEYS_MAX 1048576

@@ -336,6 +348,7 @@ struct kvm_tdx_exit {
#define KVM_EXIT_X86_BUS_LOCK 33
#define KVM_EXIT_XEN 34
#define KVM_EXIT_RISCV_SBI 35
+#define KVM_EXIT_MEMORY_ERROR 36
#define KVM_EXIT_TDX 50 /* dump number to avoid conflict. */

/* For KVM_EXIT_INTERNAL_ERROR */
@@ -554,6 +567,8 @@ struct kvm_run {
unsigned long args[6];
unsigned long ret[2];
} riscv_sbi;
+ /* KVM_EXIT_MEMORY_ERROR */
+ struct kvm_memory_exit mem;
/* KVM_EXIT_TDX_VMCALL */
struct kvm_tdx_exit tdx;
/* Fix the size of the union. */
--
2.17.1